The present invention relates to the use of tertiary amino alkyl amides as catalysts for producing polyurethane foams.
The present invention relates to tertiary amino alkyl amide catalysts for producing polyurethane foams. Polyurethane foams are widely known and used in automotive, housing and other industries. Such foams are produced by reaction of a polyisocyanate with a polyol in the presence of various additives. One such additive is a chlorofluoro-carbon (CFC) blowing agent that vaporizes as a result of the reaction exotherm causing the polymerizing mass to form a foam. The discovery that CFCs deplete ozone in the stratosphere has resulted in mandates diminishing CFC use. Production of water blown foams, in which blowing is performed with carbon dioxide (CO2) generated by the reaction of water with the polyisocyanate, has therefore become increasingly important. Tertiary amine catalysts are typically used to accelerate blowing (reaction of water with polyisocyanate to generate CO2) and gelling (reaction of polyol with isocyanate).
The ability of the tertiary amine catalyst to selectively promote either blowing or gelling is an important consideration in selecting a catalyst for the production of a particular polyurethane foam. If a catalyst promotes the blowing reaction to a too high degree, much of the CO2 will be evolved before sufficient reaction of isocyanate with polyol has occurred, and the CO2 will bubble out of the formulation, resulting in collapse of the foam. A foam of poor quality will be produced. In contrast, if a catalyst too strongly promotes the gelling reaction, a substantial portion of the CO2 will be evolved after a significant degree of polymerization has occurred. Again, a poor quality foam will be produced, this time characterized by high density, broken or poorly defined cells, and other undesirable features.
Tertiary amine catalysts generally are malodorous and offensive and many have high volatility due to their low molecular weight. Release of the tertiary amine during the foam processing may present significant safety and toxicity problems, and release of residual amine from customer products is generally undesirable.
Amine catalysts which contain amide functionality derived from carboxylic acids with long chain alkyl groups (C6 or higher) and fatty acids have an increased molecular weight and hydrogen bonding ability and reduced volatility and odor when compared with related structures which lack this functionality. Furthermore, catalysts which contain amide functionality chemically bond into the polyurethane polymer during the reaction and are not released from the finished product. Catalyst structures that embody this concept are typically of low to moderate activity and promote both the blowing (water-isocyanate) and the gelling (polyol-isocyanate) reactions to varying extents.
U.S. Pat. No. 4,242,467 discloses the use of morpholino and piperazino substituted ureas as catalysts for producing polyurethane foams.
U.S. Pat. No. 4,644,017 discloses the use of certain diffusion stable amino alkyl ureas having tertiary amino groups in the production of a polyisocyanate addition product that does not discolor or change the constitution of surrounding materials. Specifically taught are Catalyst A and Catalyst D which are reaction products of dimethylamino-propylamine and urea.
U.S. Pat. No. 4,007,140 discloses the use of N, Nxe2x80x2-bis(3-dimethylaminopropyl)urea as a low odor catalyst for the production of polyurethanes. The use of N-(3-dimethylamino-propyl)-formamide is also described as a catalyst to make polyurethane foams.
U.S. Pat. No. 4,012,445 discloses the use of beta-amino carbonyl compounds as catalysts for the production of polyurethane foams. In these catalysts, the beta-amino part is present as a dialkylamino or a N-morpholino or a N, Nxe2x80x2-piperazino heterocyclic nucleus and the carbonyl part is present as an amido or ester group.
U.S. Pat. No. 4,735,970 discloses a process for the production of cellular polyurethanes using special amine-CO2 adducts and homogeneous mixtures of these adducts. The use of N-(3-dimethylaminopropyl)-formamide is also described as a catalyst to make polyurethane foams.
U.S. Pat. No. 5,200,434 discloses the use of amide derivatives of alkylene oxide polyethers and their uses in polyurethane foam formulation.
U.S. Pat. Nos. 5,302,303, 5,374,486, and 5,124,367 disclose the use of fatty amido amines as a component necessary for the stabilization of isocyanate compositions containing flame-retardants. The shelf-life stability of isocyanate-reactive compositions is often adversely affected by the addition of flame-retardants, especially those based on phosphorous, zinc, antimony, and aluminum. The use of fatty amino amides improves the storage stability of these isocyanate mixtures.
The present invention relates to a method for preparing a polyurethane foam which comprises reacting an organic polyisocyanate and a polyol in the presence of water as a blowing agent, a cell stabilizer, a gelling catalyst, a blowing catalyst, and a tertiary amine amide catalyst composition. The catalyst composition is represented by the formula I: 
wherein A represents CH or N;
R1 represents hydrogen or 
n is an integer from 1 to 3;
R2 and R3 each represent hydrogen or a C1-C6 linear or branched alkyl group;
R4 and R5 each represent a C1-C6 linear or branched alkyl group when A represents N, or together R4 and R5 represent a C2-C5 alkylene group when A represents N; or together R4 and R5 may be a C2-C5 alkylene group containing NR7 when A represents CH or N, where R7 is selected from the group consisting of hydrogen, a C1-C4 linear or branched alkyl group, and 
and; R6 represents a C5-C35 linear or branched alkyl, alkenyl, or aryl group.
The present invention provides a reactive catalyst composition for making a water-blown flexible polyurethane foam. The catalyst composition may contain reactive Nxe2x80x94H groups from an amide functionality that can react with isocyanates causing the immobilization of the catalyst into the polyurethane polymer yielding polyurethane foams that have no amine emissions.
The use of these catalysts in conjunction with gelling or blowing co-catalysts improves physical properties and enhances processibility of the foam. As gelling catalysts, these amide catalysts in conjunction with blowing co-catalysts improve the airflow of the foam. Improved airflow means improved porosity and openness of the foam which is an indication of improved dimensional stability of the foam. As gelling catalysts, these amide catalysts in conjunction with blowing co-catalysts also improve, i.e., reduce, the force-to-crush of the foam. Reduced force-to-crush means the foam is more easily compressed which is an important advantage for minimizing foam shrinkage during processing. As blowing catalysts, these amide catalysts in conjunction with gelling co-catalysts improve the load bearing properties of the foam. That such high molecular weight compounds have good catalytic activity in the production of a polyurethane is surprising, since the prior art suggests that they will react at the time of mixing and be incorporated into the polymer matrix early in the polyurethane process thus limiting their mobility.
Another embodiment of the invention provides the reactive catalysts of the present invention as blocked with different acids to yield delay action catalysts. Such acid-blocked catalysts are expected to yield, in addition to the inherent benefits of the present composition, a delay action, which can be of advantage in flexible molded and rigid polyurethane foams.